Step 1: Current loop
$\mu = IA$ with $I = \dfrac{ev}{2\pi r}$ and $A = \pi r^2$, so $\mu = \dfrac{evr}{2}$.
Step 2: Bohr condition
$mvr = \dfrac{nh}{2\pi}$ means $vr = \dfrac{nh}{2\pi m}$.
Step 3: Combine
$\mu = \dfrac{e}{2}\cdot\dfrac{nh}{2\pi m} = \dfrac{neh}{4\pi m}$.
Step 4: Result
$\mu \propto n$, option (A). Quantities that go as $n^2$ or $1/n$ are the radius and speed in the Bohr model, not the magnetic moment.
Final Answer:
The magnetic moment is proportional to n. This is option (A).
\[ \boxed{\text{(A) }n} \]